The present invention relates to a hard coating composition including an alicyclic epoxy group-containing siloxane compound, a method for producing a siloxane hard coated article using the same, and an optical film including the siloxane hard coating cured article.
Transparent plastics have been widely used as a core material in optical and transparent display industries. In particular, transparent plastics such as PC (polycarbonate) or PMMA (polymethyl methacrylate) have been applied in displays, optical lens, transparent boards of large buildings, and automotive industries as a lightweight alternative to glass owing to the properties of high light transmittance, shatter-resistance, and high-refractive index. However, these plastic resins have the disadvantage of low abrasion resistance, because they have lower surface hardness than glass. In order to make up this disadvantage, it is an important issue to develop the hard coating technology for improving the surface hardness of plastics.
Hard coating materials are largely divided into organic, inorganic, and organic-inorganic hybrid materials. Organic materials such as acryl, urethane, and melamine have the advantages of organic materials such as flexibility and moldability, but they have low surface hardness. In contrast, silicon-based inorganic materials have the properties of high surface hardness and transparency, but they have low flexibility and moldability. Since hard coating technology requires the advantages of the both materials, organic-inorganic hybrid materials have attracted more attention than each of them. However, even though many studies have been actively made to integrate the benefits of both organic and inorganic materials into the hard coating technology, they are still unsatisfactory.
Of the conventional technologies, Japanese Patent Publication No. 2006-063244 discloses a resin composition for hard coat, which is composed of colloidal silica surface-treated with a silane coupling agent having a reactive (meth)acrylate group in the molecule, a monomer having one reactive (meth)acrylate group in the molecule or a polymer prepared by polymerization of the monomers, a bifunctional (meth)acrylate, a tri- or higher functional (meth)acrylate, a leveling agent, and a photopolymerization initiator. However, photoradical polymerization of acrylate is sensitive to oxygen, unlike polymerization of alicyclic epoxy group. Thus, when it is intended to obtain a hard coated article using acrylate, there is a disadvantage that inert gas atmosphere should be maintained.
Meanwhile, US Patent Publication No. 20120034450 discloses a surface protection film, which can be obtained by mixing an ionizing radiation curable resin, a matting agent, an ultraviolet ray absorbing agent, and inorganic fine particles subjected to hydrophobization treatment so as to prepare a resin, and then curing the resin. However, physical mixing of the ionizing radiation curable resin with the inorganic fine particles may decrease dispersibility and cause aggregation of inorganic fine particles. Transmittance is also decreased due to light scattering at the interface between the resin and the inorganic fine particles. Therefore, it is not suitable for optical protection films.
Accordingly, it is expected that development of hard coating materials with easy processability of organic materials and high light transmittance and surface hardness of inorganic materials will be essential for a wide range of applications of plastics.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.